1. Field of the Invention
The invention relates to the fabrication of field emission type electron sources and, more particularly, to a method for the fabrication of peak emitters which can be used in dense arrays of sources of this type, and is applicable notably to triode systems or to display screens.
2. Description of the Prior Art
For the fabrication of two-dimensional arrays of field emitters, the electron source is generally formed by a metallic emitter cone deposited on a substrate, surrounded by an insulating cavity formed in a thin dielectrical layer, said layer comprising, in its upper part, a thin metallic layer forming the extraction electrode. This micro-emitter is made repetitively on the substrate with a density of the order of 10.sup.6 emitters per cm.sup.2. The micro-emitters may be grouped in elementary cells, for example of the order of 10.sup.3 emitters or more per cm.sup.2, with each cell forming an emission area located at the node of a matrix network of rows of cathodes (peaks) and columns of anodes (extraction electrodes).
There are known methods for making field emitters of this type. In a first group of fabrication methods of the type described by C. A. Spindt et al. (for example, in "Journal of Applied Physics," Vol. 47, No. 12, p. 5248, December 1976) after having etched the metallic layer deposited on a layer of dielectric itself lying on a silicon substrate, the dielectric layer is etched by ionic or chemical etching, and then a thin layer is deposited on the substrate in all the holes thus formed in the dielectric layer, the sample rotating on the axis of the hole so that a cone-shaped deposit is achieved. Owing to the rotation, it is not possible to process a large number of samples simultaneously.
Another method to make peaks has been described in the prior art: this method applies a chemical etching process by the attacking of a monocrystalline substrate along preferred planes. This technique requires highly rigorous control of the chemical attacking process if it is desired to minimize the formation of "unwanted peaks" due to non-homogeneity in etching.
The prior art methods thus do not enable the simple making of an array of peak emitters.
An object of the invention is another type of field emitter fabrication method which does not have the drawbacks of the above-mentioned methods.
In particular, an object of the invention is a method for the making of electron sources and field emission cathodes by which it is possible to obtain, in a simple way, cathode peaks which are well centered with respect to the axis of the gate hole, the cathodes being formed by faceted crystalline growth, the electron sources being peaks associated with metallic layers or extractors comprising apertures, in the axis of which these peaks are located.
Another object of the present invention concerns devices using field emission cathodes which have good self-alignment characteristics, the fabrication of which is simplified by the self-alignment method of the invention.